Manly star David Williams has been suspended for rest of the NRL season for betting on games including several in which he was involved.

The former Australia and NSW winger is among five players, which includes Kiwi Slade Griffin, to receive bans for betting on NRL games following an investigation by the league's integrity unit.

The others - Ethan Lowe (North Queensland)- who has played 10 first grade games for the Cowboys since 2013 and lower graders Cody Nelson (Gold Coast) and Melbourne's Hymel Hunt and Griffin - all copped two-game suspensions.

In addition, three casual game day officials have been sacked and nine others suspended for the rest of the season for betting breaches.

Integrity unit chief Jim Doyle announced the bans on Thursday and warned that penalties for betting on NRL games will be even tougher in the future as part of a zero tolerance package of reforms.

Williams copped the heaviest penalty with Doyle saying he placed multiple bets on games, including some that he was playing in for Manly.

Griffin, a 23-year-old hooker/back rower who made his NRL debut last season and played 10 games, has not featured in first grade so far in 2014.

Lowe, Nelson, Hunt and Griffin were all suspended for betting on one game in which their club was involved, but in which they did not participate.

Doyle said an audit of betting records covering more than 1500 registered players, officials and staff found no evidence of serious abuse of the betting laws or match fixing.

But the NRL had imposed a range of suspensions, terminations and warnings to those who have breached the betting rules.

In addition to the terminations and suspensions, first and final warnings have been issued to 12 registered NRL players, staff and officials who placed small, isolated bets on rugby league matches.

They either had no connection to the matches or were unaware they were prohibited from betting on those particular matches.

None of the staff who received warnings were in senior roles or able to have any influence on the outcome of games.

In the majority of cases where warnings were issued, the bets were small - often as little as A$5 - and were not on matches involving their own club.

"There is no suggestion of match fixing or inappropriate conduct on the field by those involved, but the integrity unit is determined to protect the interests of all players, fans and members, Doyle said.